The various structures and functions of the cell are studied under the medical branch of cell biology, also called cytology. The various cell organelles and their structure as well as interaction with the environment is also a major area under the subject. Other significant areas include the metabolic processes, Signaling pathways, life cycle of cell and the interactions of the cells with each other. In vitro toxicology deals with the study of the effects of the various chemicals on the cells for the development of herapeutic drugs, agricultural chemicals and food additives etc.